1. Field of the Invention
The invention relates to automatic, premise-monitoring alarm systems such as for example burglary or burglary/fire alarm systems, and more particularly to a system for supervising the integrity of the communication path(s) that carry the alarm message data between a central alarm-message receiving station and a network of remotely-located, automatic, premise-monitoring alarm systems.
2. Prior Art
Premise-monitoring alarm systems monitor a given protected premise--say, for example, a residential home, a jewelry store, a shoe store, a bank vault, or an ATM machine and the like--for the occurrence of a given alarm event:--e.g., an unwanted intrusion, unauthorized entry or smoke and so on. Some alarm events simply correspond to a "low battery" condition in the protected-premise control unit or panel. Upon detection of a given alarm event, the automatic alarm system signals the alarm event to a central alarm-monitoring station. The central alarm-monitoring station, which may be a public or private service, may manually process the signal by an attendant who can dispatch police or fire-fighters or alert the store-owners or take whatever other steps are appropriate. Prior art automatic alarm systems have typically operated over standard voice-grade telephone lines.
It has been a problem that if the telephone line is cut or otherwise drops out of service, then the protected premise is isolated from the central alarm monitoring station, and is without means to even signal the loss of the telephone line. Indeed the central alarm monitoring station greatly desires a signal that corresponds to or indicates the loss of the telephone link between itself and the protected premise, as that is an alarm event in itself.
There are prior art systems which address this problem of loss of telephone service (or a communication link) between the protected premise and the central alarm monitoring station. As will be described further below, the prior art systems incorporate various techniques for supervising the integrity of the telephone (or communication) link. There are also, however, various shortcomings associated with the prior art systems as will also be described below. Accordingly, it is an object of the invention to overcome the shortcomings of the prior art and provide improved, communication path integrity supervision in a network system for automatic alarm data communication.